It has been well known in the art of flashlight manufacture to provide a focused beam. This has usually been accomplished by using a reflector having a generally parabolic configuration and positioning the bulb or light source at or near the focal point of the reflector.
It has also been well known to provide an adjustable focus for the flashlight beam. The preferred method of accomplishing the adjustment has been to provide a separate head which is secured upon the flashlight body by means of interengaging threads, so that rotation of the head will advance or retract it in a longitudinal direction relative to the flashlight body. The reflector is then fixedly secured to the head while the bulb or light source is fixedly secured to the flashlight body. Thus the bulb can be moved either forward or backward relative to the focal point of the reflector, thereby changing the focus of the beam.
It has also been known in variable focus flashlights to employ a reflector whose configuration does not conform precisely to that of a single parabola, but which is modified to improve the adjustability of the light beam. More specifically, the reflector is designed in such a manner that different incremental portions of the length of its reflecting surface have slightly different focal points.
A significant problem experienced in the prior art has been that, while the flashlight may be adjusted to focus the beam in a desired manner, the adjustment cannot be reliably retained. It is therefore the object and purpose of the present invention to provide a variable focus flashlight which, when adjusted to provide a desired focus of the light beam, will reliably retain that position of adjustment.